Estes (back) is scheduled to make his spring debut during Tuesday's Cactus League game against the White Sox, Jason Burke of SI.com reports.
The right-hander finished last season on the injured list due to a herniated disc in his lower back, and he ramped up slowly early on in spring training. Estes made just three appearances for the A's last season and spent most of the campaign at Triple-A Las Vegas, where he struggled to a 5.51 ERA across 80 innings.